1 in 100 times can be a problem, Alex
one petrol station even had a very old rusty kettle, which I was refused to use.
So I needed to go to the next service station, so with that in mind, my advise is.

1. Fill up long before you need to.
2 . Check to see if there is an exit point nearby.
3. Smile and be happy and don't talk Chinese
4. Carry extra fuel

And always remember you are illegally riding on the Toll road in most cases

"Arguing on the Internet is like running in the Special Olympics, even if you win you're still retarded"

Let's just say I know a guy who isn't me, who gets on the toll roads here in and around the Guangzhou/Guangdong area when he's in a rush for time or doesn't feel like riding behind trucks and muck on the regular highways. And he's been doing this for years and never had a problem. He even recently did it right in the middle of a big meeting here in Guangzhou a couple of weeks ago, the Fortune Global Business Forum where many politicians and leading industry execs were present and security was on high alert EVERYWHERE in this area - nothing happened to him at all from doing the usual dodge on/off... But, in hindsight he realizes things won't be like this forever and that things are changing and enforcement will start to become more serious in the future with the way things seem to be shaping up from a certain, let's say, political point of view.

I had another friend who rode his scooter to a relatively remote riverside beach, and three armed cops showed up in a SWAT vehicle and interrogated him intensely for half an hour in the sun. Not something that happens everyday in the area of Guangzhou he was in. Specifically it was just outside zengcheng, for those who are familiar with it.

Something that may be relative to this thread and the ramifications of law enforcement or breaking the law, etc. - here's an interesting story by the BBC to give you a glimpse of things to come... Stay safe... Eyes are watching you at all times. Not to mention their cyber controls as well and plans to have China nearly cut off from the world by making VPN usage illegal... I could go on and on.

Pro -tip - go on at nighttime. I'm a little shocked about Guangdong, I've been chased down on that expressway. Some of the expressway gate arms seem to be getting longer but who knows. On the one hand, I think providing for irontight anti motorcycle enforcement on these expressways runs into the "Not My Job" symptom of large bureaucracies which has allowed us all to skirt the rules. On the other hand, all you need at this point is one signature from above to change all that.